Get the column type of the ID field, if the entity is identified by a related entity

[floriandammeyer]

I have the following situation: one 'parent' entity has a related 'child' entity with a OneToOne relation. The child entity cannot exist without the parent entity, so the child entity derives its own identity from the parent entity. The catch: I am not using plain old integer identities, but ULIDs instead (using the according Symfony package):

// ...
use Symfony\Bridge\Doctrine\IdGenerator\UlidGenerator;
use Symfony\Bridge\Doctrine\Types\UlidType;
// ...

class Parent {
    #[ORM\Id]
    #[ORM\GeneratedValue(strategy: 'CUSTOM')]
    #[ORM\CustomIdGenerator(class: UlidGenerator::class)]
    #[ORM\Column(type: UlidType::NAME, unique: true)]
    private ?string $id;

    #[ORM\OneToOne(mappedBy: 'parent', cascade: ['all'])]
    private ?Child $child;
    // ...
}

class Child {
    #[ORM\Id]
    #[ORM\OneToOne(inversedBy: 'child')]
    private Parent $parent;
}

This seems to work fine for the most part, at least generating the migrations works fine (it creates the correct ULID database columns, especially "child.parent_id" is being created correctly as a ULID column) and also fetching a parent entity and joining the child entity into the result seems to work. So in general, Doctrine seems to be able to handle the column type of the Child entity's ID column correctly.

However, when other libraries (in this case ApiPlatform) try to automatically generate queries for the Child entity using the QueryBuilder and the ClassMetadata, the parameter type for the ID field is not being set correctly, so no result is being returned.

For example, ApiPlatform wants to create a query to fetch a single Child entity. It correctly adds a where clause for "parent" to the QueryBuilder, because this is the identifier of a Child entity. But later on, the type of that "parent" parameter is being set to the wrong value, because ApiPlatform uses $doctrineClassMetadata->getTypeOfField("parent") to get the column type, where $doctrineClassMetadata is the ClassMetadata of Child. Because there is no actual field definition for the identifier property, that method call returns null and therefore the parameter type is not being set and instead it is assumed to be the default type of integer.

I looked at the ClassMetadata class to see if this is a bug in ApiPlatform and there is another way to get the column type of the ID column in this case, but there does not seem to be one.

How do I get the column type for the ID column of Child, which should be ULID, in this case? Do I have to add some sort of column definition annotation to the ID property of my Child entity or do you have to use some other method of ClassMetadata to get the correct column type?